Electrical resistance unit



'Dec. -15, 1953 T. N. FLIGHT ETAL 2,662,958

ELECTRICAL RESISTANCE UNIT Filed Feb. 20, 1951 2 Sheets-Sheet 1 Q 1)3''(L j 7 2 s i 4 ,i I p 6 FIG. 2. 7*

Dec. 15, 1953 T, FLI ET AL 2,662,958

ELECTRICAL RESISTANCE UNIT Filed Feb. 20, 1951 2 Sheets-Sheet 2 23 [jlll Tl"Tl ll 'll j 23 I I I] I U l] U Fl L T fi Patented Dec. 15, 1953ELECTRICAL RESISTANCE UNIT Theodore Nicholas Flight, Farnham Common, andWilliam Harry Wilson, Camberley, England, assignors to The RheostaticCompany Limited, Slough, England, a British company Application February20, 1951, Serial No. 211,866

Claims priority, application France February 20, 1950 Claims. (Cl.201-74) This invention relates to electrical resistances formed fromstrip material.

An object of this invention is to provide an electrical. resistance unitwith a strip resistance form which will enable variations of resistancevalue and current carrying capacity to be made economically in varioussteps of a resi tance and to provide a maximum number of adjustmenttappings.

Another object is to form a strip by simple bending operations intoconvenient, easily handle,- elements capable of being welded to" getherto form a continuous resistance grid.

Another object is to provide a strip resistance bank as a compact easilyreplaceable unit.

The improved resistance unit of the invention comprises a plurality ofresistance elements of strip material bent to e form, each elementhaving a support strip welded thereto and each element being welded toits neighbour to form a continuous electrical path and interlockingceramic bobbins on a pair of metal tie rods to support the resistanceelements, with flanges on the ceramic bobbins projecting between theconvolutions of the elements to give support against vibration.

The invention is illustrated in the accompanying drawings in whichFigures 1 and 2 show one strip element, Figure 3 is the elevation of anassembly of 12 such elements into a bank, Figure 4 is a sectional planof a part of one bank (enlarged), and Figure 5 is an elevation of onebank in the resistance frame of Figure 6 cut across line AA. Figure 8shows three such banks mounted into a complete resistance frame.

Referring to Figure 1, a strip of resistance material l is bent twice at2 and 3 so as to leave the ends t and 5 pointing in opposite directions.One end i is left straight while end 5 is cranked to the same dimensionas the Width of bends 2 and 3. The end 5 is then in line with thestraight end 01' the commencement to the next element, Each end of thestrip element is pierced by a tap ping or terminal hole (3. Strip l isattached to the resistance strip by spot welding and forms in knownmanner the support for the element.

Referring to Figs. 3 and 4 two tie rods 8, 9 pass through the centre ofcylindrical insulators it, i I, on each of which flanges 12 are formed.Each insulator interlocks with the next on the rod by projecting pieces:13 locating in recesses i l in the opposite end of the next insulator.This is shown in section in Figure 4 which also shows the bankarrangement of two groups of elements one on each side or" the pair oftie rods.

This sectioned view also illustrates the fixing means for each elementby strip '1 clamped between adjacent insulators and supported out ofcontact with tie rod 6 by the projecting portion i3 of the insulatorwhich passes through the hole l5 in the support strip i. Terminals ortapping points I? occur at each element junction, each element beingspot welded to the next adjacent element at this point thus making eachgrid a continuous unit from end to end.

The flanges I2 formed on insulator it project slightly into the bends ofthe strip element as shown at It and give support against vibration tothe individual turns of the element at these points.

For mounting into a complete resistance frame, Figs. 5 and 6, the twotie rods 3, s are joined by a strip [9 which is cranked at one end asshown. In the cranked end is a fixing hole which aligns with thecorresponding hole in the frame member 20. This frame has a turned overflange 2i formed with recesses 22 shaped to pass the fixing nut on thetie rod end and to give support to the strip I9 as shown.

Any one bank can thus be removed from a complete resistance frame byfirst disconnecting any electrical connection, removing the fixing bolts23 and dropping the complete bank out of the supporting frame 28.

We claim:

1. An electrical resistance unit comprising a series of interconnectedresistance elements forming a resistance grid, each element formed froma strip of resistance material bent natwise so as to form an 8-shapedstrip viewed edgewise of this strip, the adjacent ends of adjacent S-shaped resistance elements being welded together to provide a continuouselectrical path, a support strip Welded to each element and projectingfrom the plane of the grid, a metal ti rod extending through the supportstrips, inte cking cylindri-- cal insulators mounted on the tie-rod forinsulating the rod from the support strips associated therewith, andspaced flanges on the insulators between which the convolutions of theresistance elements extend for supporting said elements againstvibration, said tie-rod extending parallel to the resistance grid in adirection opposite to that of the convolutions of the elements.

2. An electrical resistance unit comprising a series of interconnectedresistance elements forming a resistance grid, each element formed froma strip of resistance material bent fiatwise so as to form an S-shapedstrip viewed edgewise of this strip, each s-shaped element beingreversed with respect to adjacent S-shaped elements so that adjacentends of adjacent elements are on the same side of the grid, said endsbeing Welded together to provide a continuous electrical path, two rowsof support strips on one side of the unit projecting from the plane ofthe grid, one support strip being welded to each element, a metaltie-rod extending through each row of support strips, and interlockingcylindrical insulators mounted on said rods for insulating the rods fromthe support strips associated therewith, said tie-rods extendingparallel to each other and to the resistance grid in a directionopposite to that of the convolutions of the elements.

3. An electrical resistance unit as claimed in claim 2, in which theends of each S sha-pad element extend beyond the bends of the element,and in which the-adjacent welded ends of adjacent elements are formed toprovide electrical taps.

4. An electrical resistance unit comprising a series of interconnectedresistance elements iorming a resistance grid, each element comprising aflattened S-shaped member formed irom a strip of resistance materialbent fiatwise and having two bends, the adjacent ends 10:" adjacents-shaped resistance elements being welded together to provide acontinuous electrical path, a support strip welded't-o each'elementandprojecting from the plane of the grid, a metal tie-rod extending throughat least-some of said supper strips, and a-series of interlockingcylindrical insulators mounted on the rod :for insulating the rod fromthesupport strips associated therewith, each insulator including anaxial recess on one side and an axial projection on its other sidefitting in the recess of the adjacent insulator, each support striphaving an opening through which an insulator projection extends, saidtierod extending parallel to the resistance grid in a direction oppositeto that of the convolutions of the elements.

5. An electrical resistance unit comprising a series of interconnectedresistance elements forming a resistance grid, each element formed froma strip of resistance material bent flatwise so as to form an S-shapedstrip viewed edgewise of this strip, each S-shaped element beingreversed with respect to adjacent $-shaped elements so that adjacentends of adjacent elements are on the same side of the grid, said endsbeing welded together to provide a continuous electrical path, two rowsof support strips on one side of the unit projecting from the plane ofthe grid, one support strip being Welded to each element, a metal tierodextending through each row of support strips, interlocking cylindricalinsulators mounted on said rods for insulating the rods from the supportstrips associated therewith, said tie-rods extending parallel to eachother and to the resistance grid in a direction opposite to that of theconvolutions of the elements, a main frame for supporting the resistanceunit, a stripon the main frame, and a flat strip extending from the mainframe and connected to the two tie-rods, said fiat strip also engagingwith said strip on the main frame.

THEODORE NICHOLAS FLIGHT. WILLIAM HARRY WILSON.

References Gited in the file of this patent UNITED STATES PATENTS NumberName Date 2,277,912 Johnson et a1 Mar. 31, 1942 2,378,056 Wright 7. June12, 1945 FOREIGN PATENTS Number Country Date 153,908 GreatBritain Nov.10, 1921

